Composition for engine deposit removal



United This invention relates to a process for removing deposits from the combustion chambers of internal combustion engines, and to compositions of matter suitable for use in such a process.

It is well known to the art that during the operation of an initially clean internal combustion engine, deposits form an accumulate on surfaces within and adjacent to the combustion zone, such as on the cylinder head, spark plugs, piston tops, and valves. These deposits have a number of adverse effects on engine operation, for example, they cause an increase in the octane requirement of the engine, and also contribute to preignition with consequent roughness of operation. The problem of engine deposits is particularly acute when tetraethyl lead is contained in the fuel, since the deposits in this case contain an appreciable amount of lead compounds which adhere firmly to the surfaces on which they are deposited, and which contribute to shorting of the spark plugs, with consequent loss of power.

It is an object of this invention to provide a series of solvent formulations which are highly effective, when brought into contact with engine deposits containing lead, to soften and loosen the deposits to a degree such that, on starting the engine after such contacting, the deposits will break oif the surfaces to which they are attached and will be blown out the exhaust, leaving the surfaces in the combustion zone essentially free of deposits.

In my copending application United States Serial Number 622,256, now Patent No. 2,932,618, I disclose a series of engine cleaning compositions comprising a cyclic carbonate inner ester, a low boiling polar solvent, and acetic acid or a substance which decomposes to yield acetic acid. While these compositions are remarkably effective in cleaning out deposits in internal combustion engines, it has now been found that they are slightly unstable in storage. Over a period of months, a slow generation of carbon dioxide takes place, which causes an undesirable pressure build-up in sealed containers.

It is an object of this invention to provide a series of compositions which have a cleaning efliciency of the same order as the compositions disclosed in Serial Number 622,256, but which have the additional advantage of being stable in storage.

I have now found that compositions comprising a cyclic carbonate inner ester, water, and a mutual solvent for the carbonate and the water have the desired characteristics. The carbonate alone has good solvent power for engine deposits, and water alone has some solvent value, while the mutual solvent has negligible action on engine deposits. The combination of carbonate, water and mutual solvent has, however, greater solvent potency than the carbonate alone, as will be shown in more detail below. This also presents an economic advantage, since the cost of the composition is far less than that of the carbonate alone.

The preferred compositions of the present invention comprise from about 25% to about 75% by volume of carbonate, from about to about 50% water, and from about 10% to about 50% of mutual solvent. Mutual solvents useful in my new compositions include methanol, ethanol, isopropanol, acetone, dimethyl acetal,

PatentO Patented July 4, 1961 methyl ethyl ketone,and'other'water miscible polar solvents. The cyclic carbonate inner ester" has the formula:

Rio-0 R2C-O/ in which R may be hydrogen or a hydrocarbon radical. Typical of such esters are ethylene carbonate:

rho-o propylene carbonate:

H2 C O butylene carbonates:

mo-o-o Etc-'0 amylene carbonate:

H CsH1-CO 0:0 and its isomers,

H2CO and higher homologues of-the above compounds. While in the compounds specifically shown above the hydrocarbon substituents are alkyl, they may also be aryl, alkenyl, or alkaryl, for example, suitable compounds would include phenylethylene carbonate, methyl phenylethylene carbonate, or vinylethylene carbonate. I prefer to use carbonates which have a boiling point sufficiently high that they do not immediately vaporize upon introduction into the cylinders of an idling engine, since in order to make effective contact with the engine deposits, it is necessary that vthe carbonate be introduced into the cylinder as a mist which condenses on the surfaces to be treated. as a liquid film, in order to effect proper penetration of the deposits. I prefer to use propylene carbonate or higher molecular weight carbonates. If, however, the carbonate is of very high molecular weight, since its solvent power depends on the cyclic ester group, it is obvious that much larger quantities must be used in order to introduce into the engine the same number of cyclic ester groups as when using lower molecular weight esters. For this reason, I prefer that there be not more than about six to nine carbon atoms in the substituent hydrocarbon groups, although for special applications, such as when lubricity in the cleaning composition is desired, higher molecular weight esters may be used.

Typical solvent formulations according to the present invention are listed below. The invention should not be construed as being limited to these particular formulations, however, since others within the ranges of the components given above are also useful.

FORMULA III Butylene carbonate 50 Water 5 Methanol 25 FORMULA IV Propylene carbonate 25 Water 50 Isopropanol 25 FORMULA V Propylene carbonate 75 Water 13 Methanol 12 In order to illustrate the efiectiveness of the new compounds in cleaning deposits from engine cylinders, the following examples are given.

Example I A 1956 Oldsmobile automobile which had been run until an equilibrium amount of deposits had been built in the engine was tested and was found to require a 92 octane number gasoline to avoid knock. The engine was started, and throttled to a fast idling speed. The air cleaner was then removed and one pint of Formula I was dripped into the carburetor air inlet at the maximum rate which would just prevent engine stalling. The final portion of the pint was added in a slug to cause the engine to stall. The engine was allowed to stand for 30 minutes, and was then restarted and run for 30 seconds at widely varying r.p.m. When retested, the automobile was found to require only an 88.5 octane number gasoline to avoid knock, a decrease in octane number requirement of 3.5 numbers, indicating that substantially all of the engine deposits had been removed by the treatment.

Example II The above procedure was repeated on another 1956 Oldsmobile which had an octane requirement of 97.5. After the treatment a drop of 3.5 numbers to an octane requirement of 94 was noted.

Example III In order to compare the efficiency of my new compounds with the carbonate alone, the same procedure was followed, using one pint of pure propylene carbonate,

in treating a 1955 Oldsmobile having an octane requirement of 95.7 and a 195 6 Buick having an octane requirement of 99.91. In the case of the Oldsmobile, the octane requirement was reduced by 3.0 numbers, while in the case of the Buick, the requirement was reduced by only 2.1 numbers.

Example IV In an effort to determine the role of the water in cleaning engine deposits, the procedure of Example I was followed using water alone. It was found that the octane number requirement of a 1954 Oldsmobile could be reduced by 1.2 numbers by the use of water alone. When this engine was retreated with one pint of Formula I, a further reduction of 3 numbers in the octane requirement was noted, indicating that water alone had removed only a minor portion of the engine deposits.

The invention claimed is:

1. A solvent composition for the removal of lead-containing engine deposits which consists essentially of: from about 25 to about 75 volume percent of a cyclic carbonate inner ester selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and amylene carbonate; from about 10 to about volume percent of water; and from about 10 to about 25 volume percent of a mutual solvent for the carbonate inner ester and the water, said solvent being selected fiom the group consisting of methanol, ethanol, isopropanol, acetone, dirnethyl acetal and methyl ethyl ketone.

2. The composition according to claim 1 in which the cyclic carbonate inner ester is propylene carbonate.

3. A solvent composition for the removal of lead-containing engine deposits which consists essentially of about 38 volume percent propylene carbonate, about 37 volume percent water, and about 25 volume percent methanol.

References Cited in the file of this patent UNITED STATES PATENTS 1,287,589 Lewis Dec. 10, 1918 2,766,258 Malkemus Oct. 9, 1956 2,789,891 Brandes et al Apr. 23, 1957 OTHER REFERENCES The Condensed Chemical Dictionary, 5th Ed, 1956, p. 909, Reinhold Publ. Corp., N.Y. 

1. A SOLVENT COMPOSITION FOR THE REMOVAL OF LEAD-CONTAINING ENGINE DEPOSITS WHICH CONSISTS ESSENTIALLY OF: FROM ABOUT 25 TO ABOUT 75 VOLUME PERCENT OF A CYCLIC CARBONATE INNER ESTER SELECTED FROM THE GROUP CONSISTING OF ETHYLENE CARBONATE, PROPYLENE CARBONATE, BUTYLENE CARBONATE, AND AMYLENE CARBONATE, FROM ABOUT 10 TO ABOUT 50 VOLUME PERCENT OF WATER, AND FROM ABOUT 10 TO ABOUT 25 VOLUME PERCENT OF A MUTUAL SOLVENT FOR THE CARBONATE INNER ESTER AND THE WATER, SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF METHANOL, ETHANOL, ISOPROPANOL, ACETONE, DIMETHYL ACETAL AND METHYL ETHYL KETONE. 